How to 'Like-gate' with OmniAuth Facebook, Sinatra and Datamapper - ruby

Question

For an app I'm, building I need to be able to determine a Facebook user's relation to the page of which the app is being shown within. I hope to provide the following functionality:
1) If the user likes the page, direct them to another page
2) If the user doesn't like a page, direct them to another page
3) If the user is an admin of the current page, direct them to another page
The Auth Hash schema (https://github.com/intridea/omniauth/wiki/Auth-Hash-Schema) doesn't provide info of how to access user likes, or indicate a way whether they: a) Like or don't like the current page, or B) are an admin of the current page.
Furthermore I've researched around the internet but cannot find any specific Ruby or Sinatra example of how to do this. The closest that I've come to is (https://github.com/chrissloan/sinatra-book/blob/master/app.rb), however this users FBGraph (I'm using Omniauth-Facebook) and this script doesn't make any distinction between admin users of the page.
Therefore I'm wondering if my method of distinguishing between users on the page tab is inherently wrong and am wondering if there is another process of achieving the desired goals.
So in summary, I'm attempting to create:
A backend that is accessible by the app admin. When an app admin goes on the page, the admin panel is displayed.
A front end that displays whether the user has liked the page or not, and shows them specific content based upon this state - a 'like-gate'.
Thanks for reading and if you could help it would be very much appreciated.
Some code I've thought up, but from the docs I'm unsure of whether it is valid syntax or not. From begin is the experimental piece, the code above works and is currently being used.
get '/auth/:provider/callback' do
content_type 'application/json'
JSON.generate(request.env)
auth = request.env["omniauth.auth"]
puts auth
=begin
if auth['page']['admin'] == true ***not sure if admin is valid syntax***
#check user database and move to admin side
else if auth['page']['liked'] == true
#allow to download endpoint
else
auth['page']['liked'] = false
#direct to wall to like
end

Answer 1

I solved this by authorising with OmniAuth and then getting the signed_request generate from Facebook when the user opens the app on a Facebook page.